Evaluation of Hepatitis C Virus Core Antigen Assay in a Resource-Limited Setting in Pakistan

Abstract

The diagnosis of Hepatitis C virus (HCV) infection can be challenging due to its cost and a lack of access to centralized testing. There is an urgent need to develop simplified HCV testing algorithms. The aim of this study was to evaluate the performance characteristics of a Hepatitis C core antigen (HCVcAg) assay in a decentralized, resource-limited setting. This is a descriptive cross-sectional study from a highly endemic area of Karachi, Pakistan. Between October 2019 and July 2020, subjects aged 12 years and above who screened positive for HCV antibodies were simultaneously tested for HCV RNA (Xpert HCV Viral Load, GeneXpert^® IV, Cepheid, France) and HCVcAg (ARCHITECT HCV Ag assay, Abbott^® Diagnostics) to confirm active HCV infection. An Abbott ARCHITECT^® i1000SR Immunoassay Analyser was installed at a local district hospital as a point-of-care (POC) facility for HCVcAg testing, while samples for HCV RNA were tested in a central lab. Two hundred individuals (mean age 46.4 ± 14.5 years, 71.5% females), who screened positive for HCV antibody, were included in the study. HCV RNA was detected in 128 (64.0%) while HCVcAg was reactive in 119 (59.5%) cases. Performance of the Immunoassay Analyser was excellent with a higher throughput and quicker readout value compared to the GeneXpert System. The sensitivity and specificity of HCVcAg (≥10 fmol/L) at HCV RNA thresholds of ≥12 was 99.1% (95% CI: 95-100%) and 87.6% (95%CI: 78.4-94%). A strong agreement was observed between the HCVcAg assay and HCV RNA. The ARCHITECT HCV Ag assay showed high sensitivity and specificity compared to HCV RNA in a decentralized, resource-limited setting. It can therefore be used as a confirmatory test in HCV elimination programs, particularly for low-income countries such as Pakistan.

Keywords: GeneXpert® IV; HCV Core antigen; Hepatitis C; dededecentralized.

Figure 1

Representation of the results of all study samples (n = 200).

Figure 2

Relationship between the difference in HCV RNA and HCV core antigen (cAg), plotted against the mean of the two measurements in a Bland–Altman plot. The three lines in Figure represent mean of differences-called bias and the other two lines are limits of agreement mean +1.96 SD and mean −1.96 SD. [The x axis represents the logarithmic mean levels of RNA and HCVcAg after conversion of HCVcAg to HCV RNA. The y-axis represents the logarithmic difference of RNA and HCVcAg].